Applicable Systems
Copeland Scroll Compressor (CoreSense/Comfort Alert)
Symptoms
The CoreSense/Comfort Alert module LED flashes 5 times, indicating a Motor Protector Trip. The compressor internal motor overload protector has opened, shutting down the compressor due to excessive motor winding temperature or current.
Possible Causes
- Compressor operating beyond design conditions (high compression ratio, high ambient)
- Refrigerant charge low causing insufficient motor cooling
- Liquid refrigerant flooding back to the compressor (floodback)
- Compressor bearings worn causing excessive mechanical load and motor current
- Dirty condenser or failed condenser fan causing high discharge temperatures
Troubleshooting Steps
- Step 1: Allow the compressor to cool for at least 2 hours before attempting restart
Motor winding temperature drops below the protector reset threshold - Step 2: Check the suction superheat to ensure no floodback is occurring
Superheat is between 10-20F at the compressor suction - Step 3: Verify the condenser is clean and all condenser fans are operational
Condenser approach temperature is within design (typically 10-20F) - Step 4: Check the refrigerant charge by measuring subcooling at the condenser outlet
Subcooling matches the system design specification - Step 5: Measure the compressor motor current under load and compare to nameplate
Running current is below the nameplate FLA (Full Load Amps)
How to Reset
To reset: 1) Fix the root cause (charge, airflow, floodback). 2) Allow the motor to cool. 3) The internal protector will auto-reset when the winding temperature drops. 4) If the module requires manual reset, press the reset button. Caution: Repeated motor protector trips indicate a serious system problem; continued resetting will damage the motor windings.
Frequently Asked Questions
- Q: What is the internal motor protector?
Copeland scroll compressors have an internal line-break overload protector embedded in the motor windings. It opens when the winding temperature or current exceeds safe limits. It auto-resets when the winding cools, typically after 1-2 hours.
- Q: Why does low refrigerant charge cause motor overheating?
The refrigerant gas flowing through the compressor motor helps cool the windings. With low charge, the gas mass flow is reduced, providing insufficient cooling. The motor temperature rises until the internal protector trips.
Source: Copeland Application Engineering Bulletin AE4-1303, CoreSense Diagnostics
Category: Refrigeration